Fluid sealing and burr elimination projectile for perforator guns



March 23, 1954 p DUBOST 2,672,814

FLUID SEALING AND BURR ELIMINATION PROJECTILE FOR EERFORATOR. GUNS Filed 001?- 7, 1949 FIGJ.

l5 I5 I ,7

' INVENTOR. PIERRE 'DUBOST WMZL$$I M HIS ATTORNEYS.

Patented Mar. 23, 1954 FLUID SEALING AND BURR ELIMINATION PROJECTILE FOR PERFORATUR GUNS Pierre Dubost, Houston, Tex assignor to Sohlumberger Well Surveying Corporation, Houston, Tex., a corporation of Delaware Application October 7, 1949, Serial No. 120,084

2 Claims.

The present invention relates to gun-type apparatus for perforating the metallic casings usually inserted in bore holes drilled into the earth, and more particularly to a new and improved form of projectile which is simple in construction and highly effective in operation.

Gun perforating apparatus employed heretofore for perforating well casings has usually comprised an elongated gun body adapted to be lowered into a bore hole and having lateral bores formed therein adapted to receive casing perforating projectiles. The projectiles were usually formed with a cylindrical body and a sharply pointed nose and stoppers'were inserted in the gun bores ahead of the projectiles in an effort to seal the powder chamber behind the projectile from the bore hole fluid. Sometimes soft metal plugs were placed in the bore between the nose of the projectile and the stopper to prevent the formation of burrs in the casing when pierced by the projectile.

Apparatus of the type outlined briefly above has not been found to be entirely satisfactory. For one thing, a large amount of rubber was used in the stoppers in an effort to insure maximum effectiveness, so that an excessive amount of trash remained in the bore hole after the projectile was fired. Further, it was found that even large stoppers permitted some leakage of the bore hole fluid into the powder chamber under the high pressures and temperatures encountered in deep wells, particularly where the gun bore had become eroded from constant use. In addition, it was found that the soft metal plugs caused considerable damage to the gun bore and decreased the penetrating power of the projectile. Moreover, three time consuming operations were required to place a projectile, a burr eliminating plug and a stopper in each gun bore.

In an effort to overcome certain of the abovenoted disadvantages, it has been proposed to employ a projectile of smaller diameter than the gun bore having its rear end mounted in a cup shaped element of soft metal and of the same diameter as the gun bore. It was found, however, that the cup shaped element tended to damage the gun bore just as the soft metal plugs did. Further, there was some likelihood that the soft metal cup shaped element would plug the perforation made by the projectile.

It is an object of the present invention, accordingly, to provide a new and improved projectile for gun perforators and the like which combines stopper and burr elimination features yet may be loaded as a unit in a gun bore in a single loading operation.

Another object of the invention is to provide a new and improved projectile for gun perforators and the like which includes means for eliminating burrs formed in a perforating operation, in a highly effective manner without damaging the gun bore or impairing the effectiveness of the perforating operation.

Still another object of the invention is to provide a new and improved gun perforating projectile of the above character in which the burr eliminating means serves both to center the projectile in the bore and to increase the depth of penetration thereof.

Yet another object of the invention is to provide new and improved gun perforating apparatus having stopper means for sealing a powder chamber in the gun from the bore hole fluid, which is highly effective under extreme pressures and temperatures, even when the gun bore is eroded.

According to the invention, a composite projectile is provided which comprises a casing piercing member of lesser diameter than the gun bore which carries a burr elimination member of substantially the same diameter as the gun bore at the rear end thereof, together with a bore stopper member located ahead of the burr elimination member. The burr elimination member surrounds the rear end of the casing piercing member and is made of hard metal so that it will flatten the burrs formed during the perforating operation upon impact therewith. It is designed to shatter upon impact with the casing, forming small pieces which drop harmlessly to the bottom of the bore hole and it may be suitably weakened to insure this result, if desired.

The bore stopper member, which is made of flexible material such as rubber, for example, surrounds the casing piercing member and is tightly fitted into the space between the latter and the interior wall of the gun bore. In one embodiment, it is provided with a flanged forward portion which is adapted to be forced more tightly into engagement with the interior wallof the gun bore as the pressure of the bore hole fluid increases, thereby effectively sealing the gun bore from the bore hole liquid.

According to another embodiment, a soft metal ring is fitted at the rear of the stopper member which is adapted to be forced more tightly into engagement with the wall of the gun bore as the pressure of the bore hole fluid increases. It thus prevents the stopper member from flowing around the burr elimination member in an eroded gun bore so that the bore seal is effectively maintained.

Additional objects and advantages of the inven tion will be apparent from the following detailed description of several typical embodiments, taken in conjunction with the accompanying drawings, in which:

Fig. l is a schematic diagram, partly in longitudinal section, of a composite gun perforating projectile constructed according to the invention;

Fig. 2 illustrates schematically a projectile of the type shown in Fig. l in position in a gun bore of a perforating gun; and

Fig. 3 is a schematic diagram, partly in longitudinal section, of another embodiment of the invention which is particularly useful in eroded gun bores.

In the form of the invention shown in Fig. 1, the composite projectile comprises a casin pierce ing member including a rear cylindrical portion ll of lesser diameter than the gun bore and a sharply pointed nose portion I2. Surrounding the rear portion H of the casing piercing member lfl is a substantially cylindrical sleeve iii of substantially the same diameter as the gun bore, having an interior shouldered portion l4 on which the rear. end of the casing piercing member It} isadapted to be seated.

The sleeve l3 constitutes a burr elimination member and it is made of sufficient thickness and of a suitably hard metal to flatten the burrs surrounding a casing perforation upon impact therewith. Thematerial comprising the sleeve I3 should also be brittle so that the sleeve l3 will shatter into small pieces upon impact with the casing. Materials having suitable hardness and brittleness for this purpose may include cast iron and certain brittle steels, for example. If desired, the sleeve [3 may be suitably weakened as by'forming circumferential grooves i5 therein to facilitate its destruction upon impact.

Mounted on the casing piercing member i0 is a-tubularstopper member it made of flexible material such as rubber, for example. Preferably, the stopper member I6 is bonded both to the casing piercing member l0 and to the forward edge of the burr elimination member 13. The stopper member 16 is provided with a forwardly and outwardly extending flange I! which forms an effective bore seal as described below.

The loading of a gun perforator with composite projectiles of the type shown in Fig. 1 may be performed simply and quickly. All that is involved is the insertion ofa composite projectile as a unit into a bore ill of the gun l9, as shown inF-ig'. 2; Only one operation is required to load a. gun bore, therefore.

In operation, the gun I9 is lowered into a well. As the pressure of the fluid in the well increases, the flange H on the stopper member If; is forced more and more tightly into engagement with the inner wall of the gun bore 18, thus maintaining an effective seal between the powder chamber and the bore hole fluid.

When the desired depth for perforation is reached, the powder charge 2| in the chamber 20 is ignited in any known manner and the composite projectile is fired from the gun l9, causing the casing piercing member In to perforate the well casing (not shown). Since the total cross sectional areaof the casing piercing member Ill and. the burr elimination member I3 is greater than. the cross, sectionalarea. of the. former alone. it, will be understood that. a. greater force will be applied. tov the composite projectile than would be applied to the casing piercing member I 0 alone. Hence, the composite projectile will have better perforator.

4 penetrating power than the casing piercing member l 0 without the member I3.

The sleeve l3 forces the stopper member l6 against the well casing (not shown) causing it to disintegrate and fall harmlessly to the bottom of the well. The sleeve [3 is then driven against the burrs surrounding the perforation in the easing (not shown), thereby flattening them. The force of the impact shatters the brittle sleeve l3 into many small pieces which fall harmlessly to the bottom of the Well.

As shown in Fig. 2, the burr elimination member l3 centers the casing piercing member [0 in the bore l8 prior toq'detonation of the explosive charge 2 I Also, since the burr elimination member l3 has a relatively large area exposed to the forces developed by the explosion, it will not only remain attached to the casing piercing member 10 until the casing is reached but will increase the penetrating power of the member I0. Further, the burr elimination member l3, which is of substantially the samediameter as the gun bore 18-, will not appreciably damage the latter since it is made of hard material.

If erosion of the gun bore I8 has taken place as a result of constant. use, it will be understood that the burr elimination member 13 will not fit so tightly therein as. before. In such case, it has been founclthat the stopper member l5 may flow around the burr elimination member I3 under extreme bore hole pressures and temperatures and may finally become sheared. If this. occurs, the bore hole fluid mayleakinto the explosive chamber 20'. This can be. avoided by using a composite projectile of the type shown in Fig. 3..

In Fig. 3:, the casing piercing member It and the burr eliminating member 13' are the same as in Fig. 1. However, the stopper member isnot flanged at its forward end but is provided with a metal ring 22. at its rear end made of soft metal such as annealed copper, for example. The. ring 2.2 has an. inwardlyz extending flange. 2.3. lying between the members I13 and 16.. With this: construction, the hydrostatic. pressure of the bore hole fluid acting against. the stopper member forces the ring 22' tightly against the eroded gun bore :8, thus preventing the stopper member Hi from flowing around the member. |3.. Preferably, the stopper member [6: is bonded both to the ring 22 and to. the member [31.2 Thus, the composite projectile may be inserted as a. unit into the gunbore- 1-8.-

The invention thus provides a novel and highly efiective composite projectile which can be assembl'ed quicklyand easily ina bore of a gun Byvirtueof the construction described above, an effective seal is maintained between the gun bore and. the bore hole fluidand burrs formed during perforating operations are eliminated. Moreover, these desirable features may be secured. without damaging the gun bore or. impairing. the efiectiveness of. the perforating operation.

The specific. embodiments disclosed herein are merely illustrative and are not to. be regarded er havin an inn r shouldenedportion against.

which the rear end of said body is adapted to be seated, a second flexible sleeve member tightly fitted on said body ahead of said first sleeve member and a ring of soft metal around the rear portion of said second sleeve member and having a flange thereon extending between said first and second sleeve members. a

2. A casing perforating projectile as set forth in claim 1, said ring of soft metal being bonded to the second sleeve member, and said second sleeve member being bonded to the first sleeve member, thereby to form a composite projectile assembly.

PIERRE DUBOST.

References Cited in the file of this patent UNITED STATES PATENTS Number OTHER REFERENCES Ser. No. 276,093, Schlumberger (A. P. 0.). published May 4, 1943, now abandoned. 

